Dry heaving

Question
I have been running on and off since 4 years ago when I ran cross-country in highschool, and I recently started to run at least 3 miles a workout to get ready for a 5k. When I ran the 5k I started dry heaving on and off the last mile to the point where I slowed down some. The last 200 meters I tried to kick but each time I tried to sprint I started to gag and had to slow back down, I couldn't finish strong at all, I had to jog it in which is something I never did. How can I race without worrying about dry heaving holding me back. Any help would be appreciated. And why is this happening.

Answer
Hi Timmy
Your problem is somewhat common when your running a pace which is a little over your head and then you push even harder at the end.You just have to watch your comfort level toward the end and don't push so hard.Even pace all the way produces the best results.To answer the question on why........
Here is one thing which i'm sure is contributory that i can comment.As far as the dry heaves go this is a fairly common thing when you push to hard.It is a very fine line when this occures.The factors probably responsble include:decreased blood flow to the intestine and retention of food in the stomach during running;build up of acid and metabolic products in the blood;and overactivity of the vagus and sympathic nervous stsytems which stimulat the vomiting center.

All the best Timmy

John